BRPI0708630B1 - lubricating antioxidant compositions employing synergistic organotungstate component - Google Patents

Abstract

Lubricating antioxidant compositions employing synergistic organotungstate component. The invention relates to an additive for enhancing antioxidant capacities in a lubricant composition, wherein the lubricant composition is based on a larger amount of a lubricating oil and 0.1 - 5.0 weight percent of an additive, the additive. including a secondary diarylamine and an organoammonium tungstate.

Description

LUBRICANT ANTIOXIDANT COMPOSITIONS USING SYNERGISTIC ORGANOTUNGSTATO COMPONENT

FIELD OF THE INVENTION The present invention relates to lubricating compositions for imparting improved antioxidant properties. In particular, the invention relates to novel antioxidant compositions containing diarylamine antioxidant (s) in combination with organoammonium tungstate compound (s), which demonstrate a synergistic combination providing significantly higher antioxidant activity than either component separately. when used in lubricants.

BACKGROUND OF THE INVENTION

Motor oils work under strong oxidative conditions. Oxidative breakage of engine oil creates sediment and deposits, deteriorates oil viscosity characteristics, and produces acidic bodies that corrode engine parts. To combat the effects of oxidation, motor oils are formulated with a set of antioxidants that include hindered phenols, aromatic amines, zinc dithiophosphates (ZDDP), sulfurized hydrocarbons, non-metal and dithiocarbamates and organo-molybdenum compounds. Particularly effective antioxidants are alkylated diphenylamines (ADPAs) and ZDDPs. In combination, these two compounds provide most of the antioxidant capacity in motor oils in current practice. In addition, ZDDP is the leading source of wear protection for motor oils. However, the use of ZDDP in engine oils is decreasing due to the effect of phosphorus poisoning on the discharge aftertreatment catalyst. In addition, sulfur levels in engine oils are also declining due to the effect of sulfated ash discharge aftertreatments. Thus, there is a need for effective antioxidant chemistry that can reduce or eliminate the need for sulfur and phosphorus containing antioxidants and anti-wear additives.

In US patent application 2004/0214731 Al, Tynik discloses that organoammonium tungstate compounds are effective anti-wear additives without contributing phosphorus or sulfur to a lubricant composition. The invention herein reveals that unlike ZDDP, such organoammonium tungstate compounds individually do not effectively inhibit the oxidation of lubricant compositions. However, in the presence of secondary diarylamines, organoammonium tungstate compounds act synergistically to provide greatly improved oxidation control over either component separately. Thus, organoammonium tungstates represent a technology that will reduce or eliminate the need for phosphorus and sulfur-containing additives such as ZDDP.

SUMMARY OF THE INVENTION

It has now been found that a combination of (A) secondary diarylamine antioxidant (s) and (B) organoammonium tungstate compound (s) provide significantly improved anti-oxidation performance for lubricating oil compositions. Tungstate acts synergistically with the antioxidant (s), providing greatly improved oxidation control over that provided by either component separately.

DETAILED DESCRIPTION

Secondary diarylamines used in the present invention should be soluble in the formulated oil packaging or packaging concentrate: wherein R1, R2, R3 and R4 individually independently represent hydrogen, alkyl, aralkyl, aryl and alkaryl groups having 1 to about 20 carbon atoms. carbon by each group. Preferred groups are hydrogen, 2-methylpropenyl, 2,4,4-trimethylpentenyl, styrenyl and nonyl. The cyclic structure can be represented when X is (CH2) n / SouOenéOa2. Examples of such cyclic compounds are carbazoles, acridines, azepines, phenoxazine and phenothiazines. Non-cyclic secondary diarylamines are preferred.

For this invention, organoammonium tungstates are prepared by reacting acidic forms of organo and oxotungsten compounds containing amines or basic nitrogen. Possible sources of tungsten are listed, but not limited to those in Table 1. Of these sources, tungstic acid, ammonium tungstate, ammonium paratungstate, and ammonium metatungstate react directly with amines. Tungsten trioxide is a basic anhydride that must be hydrolyzed to produce tungstic acid. A preferred method of hydrolyzing tungsten trioxide is described by Tynik, US Patent Application 2004/0214731 A1, incorporated herein by reference. In this method, tungsten trioxide is hydrolyzed with 2 equivalents of caustic to produce metal tungstate hydrate which is then acidified with 2 equivalents of acid to form tungstic acid. Alternatively, tungstic acid may be produced directly from the acidification of commercially available metal tungstates such as sodium tungstate dihydrate and calcium tungstate. Polyoxotungstates, [WxYy (OH) z] n -, are formed when less than 2 acid equivalents are used to neutralize metal tungstates, and may also be used to form organoammonium tungstates.

Table 1: Tungsten Sources For purposes as a tungsten source reagent, reactive amines will be defined as compounds containing basic nitrogen that can be measured by ASTM D 28 96, Standard Test Method for Base Number of Petroleum Products by Potentiometric Perchloric Acid Titration . Much of the amine compounds are expected to undergo an acid / base reaction with the tungsten sources described above. The main requirement of amine is to make oil soluble tungstate products. Alkyl mono amines of US patent application 2004/0214731 A1 and polyamine dispersants, which are essential components used in motor oils, are preferred.

Alkyl mono amines consist of the formula RsR6 NH, wherein R5 and R6 are identical or different and selected from the group consisting of hydrogen, straight or branched saturated or unsaturated alkyl group, containing from 8 to 40 carbon atoms, or alkoxy groups containing from 1 to 12 carbon atoms. More preferred is the straight and branched C 1-14 alkyl di (alkyl) amine, also known as 'di-tridecylamine', available from BASF Corporation, and di-n-octylamine.

Polyamine dispersants are based on polyalkenylamine compounds: wherein R7 and Rs are independently hydrogen, straight or branched alkyl groups containing from 1 to 25 carbon atoms, alkoxy groups containing from 1 to 12 carbon atoms, alkylene groups containing from 2 to 6 carbon atoms and hydroxyl or amino alkylene groups containing from 2 to 12 carbon atoms, x is 2 to 6, preferably 2 to 4, and n is 0 to 10, preferably 2 to 6. Triethylene tetramine, tetraethylene pentamine are particularly preferred. and mixtures thereof, wherein R7 and R8 are both hydrogen, x2a3en2.

Polyamine dispersants are prepared by reacting polyalkenylamine compounds with carboxylic acids (ROOH) or reactive derivatives thereof; alkyl or alkenyl halides (RX) and alkyl or alkenyl substituted succinic acid to form respectively carboxylic acid amides, hydrocarbyl substituted polyalkenylamines and succinimides: Typical carboxylic acid amides are those disclosed in ÜS 3,405,064, the disclosure of which is incorporated by reference. The products are monocarboxylic acid amides as shown above or polycarboxylic acid amides, in which more than one of the primary and secondary amines (-NH and NH2) are transformed into carboxylic acid amides. R 9 groups in carboxylic acid are 12 to 250 aliphatic carbon atoms. Preferred R9 groups contain from 12 to 20 carbon atoms and polyisobutenyl (PIB) chains containing from 72 to 128 carbon atoms.

Typical hydrocarbyl substituted polyalkenylamine compounds are disclosed in US Patent 3,574,576, the disclosure of which is incorporated by reference. The products are mono or poly substituted. Hydrocarbyl groups, R 1, are preferably 20 to 200 carbon atoms. Particularly preferred halides used in the formation of hydrocarbyl polyalkenylamine compounds are polyisobutenyl chlorides containing from 70 to 200 carbon atoms.

Preferred polyamine dispersants of the present invention are succinimides which are mono- or bis-substituted and more preferred are monosubstituted succinimides: wherein R11 is from 8 to 400 carbon atoms and preferably from 50 to 200 carbon atoms. Particularly preferred are succinimide dispersants which are polyisobutenyl derivatives having molecular weights ranging from 800-2,500 grams per mol and polyethylene amines such as triethylene tetramine, tetraethylene pentamine and mixtures thereof. The specific commercial example of monosubstituted succinimide dispersant is Chevron ORONITE® OLOA 371 and OLOA 11,000, concentrated version of OLOA 371. The specific example of bisubstituted succinimide dispersant is HiTEC® 644 provided by Afton Chemical.

Another type of dispersant is grafted polyamine with viscosity index (VI) enhancers. Several patents disclosing the preparation of such compounds are available. A sample of such patents which are hereby incorporated by reference are US Patents: 4,089,794; 4,171,273; 4,670,173; 4,517,104; 4,632,769 and 5,512,192. The typical preparation involves pre-grafting olefin copolymers with ethylenically unsaturated carboxylic acid materials to produce an acylated VI enhancer. The acyl groups are then reacted with polyamines to form carboxylic acid amides and succinimides.

Another class of polyamine dispersants is the Mannich base composition. Typical Mannich bases which may be used in the present invention are disclosed in US patents 3,368,972, 3,539,663, 3,649,229 and 4,157,309. Mannich bases are typically prepared from alkylphenol having alkyl groups of 9 to 200 carbon atoms, and aldehydes such as formaldehyde and polyalkenylamine compounds such as triethylene tetramine, tetraethylene pentamine and mixtures thereof. The preferred method of preparing organoammonium tungstates from alkyl mono amines involves a two-phase reaction of aqueous tungstic acid solution with alkyl mono amine preferably diluted in organic solvent or diluent oil as described in Tynik, patent application. US 2004/0214731 A1. After an appropriate amount of mixing and heating, the phases are allowed to separate and the crude organoammonium oxotungstate product is isolated. The product is vacuum distilled to remove traces of water and organic solvent if used. The preferred stoichiometric ratio of tungstic acid to alkyl monoamine is 0.5 to 1.0. The most preferred stoichiometry is 1 mol of monoamine per 1 mol of tungstic acid.

For dispersing tungstates, a preparation method involves a two-phase reaction of aqueous tungstic acid solution with polyamine dispersant, the polyamine dispersant preferably diluted in oil. After an appropriate reaction time, water is removed by vacuum distillation. The preferred stoichiometric ratio of tungstic acid to amine nitrogen is 0.1 to 1.0, preferably 0.5 to 1.0 and more preferably 0.8 to 1.0. The second method of preparation involves a three phase reaction consisting of polyamine dispersant, solid tungsten acid, WO3.H2O and water. After appropriate reaction time, water is removed by vacuum distillation. The preferred stoichiometric ratio of tungstic acid to aminic nitrogen is 0.1 to 1.5, preferably 0.5 to 1.0 and more preferably 0.8 to 1.0. The additive combination of the invention is used together with a lubricating oil to form a lubricating oil composition, wherein the lubricating oil comprises at least 50 weight percent thereof. The combination of secondary diarylamine component and organoammonium tungstate is particularly useful for enhancing antioxidant properties when the total amount of these two components as part of a lubricant composition ranges from 0.10 - 5.0 weight percent. Lubricating compositions containing 0.1 - 4.0 mass percent (1,000 - 40,000 ppm) of secondary diarylamine component and 0.005 - 0.5 mass percent (50-5,000 ppm) of tungsten from tungstate are particularly useful. of organoammonium. Preferably, the lubricating compositions contain 0.5 - 2.0 mass percent (5,000 - 20,000 ppm) of secondary diarylamine component and 0.05 - 0,3 mass percent (500 - 3,000 ppm) of tungsten from of organoammonium tungstate. The invention also comprises lubricating compositions wherein the secondary diarylamine: organoammonium tungstate ratios are 20: 1 to 1:30 by mass. Preferably, the ratios are 9: 1 to 1: 9 by mass, and more preferably 3: 1 to 1: 3. In terms of secondary diarylamine versus tungsten content, the ratios are 70: 1 to 1: 3 by mass. Preferably, the ratios are 30: 1 to 1: 1 by mass, and more preferably 16: 1 to 2: 1. The oil component of the present invention may be one or a combination of any viscosity mineral or synthetic lubricating oils used as lubricating base materials. Mineral oils may be paraffinic or naphthenic. Paraffin oils may be Group I solvent-refined base oils, Group II hydrocracked base oils and Group III high viscosity index hydrocracked base oils. Synthetic oils may consist of group IV polyalphaolefin (PAO) type and group V synthetic oils, which include diesters, polyol esters, polyalkylene glycols, alkylbenzenes, organic phosphoric acid esters and polysiloxanes.

In addition to secondary diarylamine and organoammonium tungstate, the lubricating composition may also include additional antioxidants, additional dispersants and detergents, additional anti-wear additives including ZDDP, friction modifiers, viscosity modifiers, pour point depression media, antifoam additives and demulsifiers.

To illustrate various organoammonium tungstate compositions that may be used in the invention, the following preparation methods are provided as illustrative examples. The following examples are provided for illustrative purposes only and are not intended to place any limitation upon the scope of the invention where such scope is set forth only in the claims.

Example 1 Preparation of straight and branched C 1-4 di (alkyl) ammonium tungstate Sodium tungstate dihydrate (132.0 g) is dissolved in 250.0 g of water and then slowly acidified with 138.7 g of a 26.8% sulfuric acid solution. A solution of branched and linear C 1-4 di (alkyl) amine (97.7%; 157.9 g) in 150 g of heptanes is then charged as a whole into the cloudy, light yellow tungsten solution under vigorous stirring. . The reaction mixture is then heated to reflux for 30 minutes, after which the aqueous phase is separated and the organic phase is transferred to a rotary evaporator where the solvent is removed. Residual solids are removed by filtration. The product is then obtained as a light yellow viscous oil. Tungsten content was determined to be 29.5 weight percent.

Example 2 Preparation of Ammonium Tungstate from PIB Monosuccinimide Polyamine Dispersant

Sodium tungstate dihydrate (33.0 g) is dissolved in 75.0 g of water and then slowly acidified with 35.3 g of a 28% sulfuric acid solution. A solution of 105.8 g of a monosuccinimide dispersant (OLOA® 371; 46.7% active in process oil; TBN = 53.0) and 65.0 g of process oil is heated to 50 ° C and loaded as a whole into the cloudy, light yellow tungsten solution under vigorous stirring together with 4 drops of Antifoam B®. The reaction mixture is then heated at reflux until approximately 75% of the water is distilled. Vacuum is then applied slowly and the temperature is raised to 125 - 130 ° C and held for 30 minutes. The reaction mixture is then hot filtered through diatomaceous earth providing dark, viscous light amber oil. Tungsten content was determined to be 9.67 weight percent.

Example 3 Preparation of ammonium tungstate from PIB (polyisobutylene) mono-succinimide polyamine dispersant To a solution of 46.9 g of dispersant (OLOA® 11000; 71.2% active in process oil; TBN = 76.3 ) and 64.5 g of process oil are charged 16.0 g of tungstic acid and 16.0 of water. The stirred solution is then heated at 100 ° C for 10 minutes and then slowly heated at 160 ° C for 1 hour while collecting the distillate. When distillation ceases, vacuum is applied to the system and the reaction continues at 160 ° C with stirring until the reaction mixture turns brown. It is then hot filtered through diatomaceous earth. Tungsten content was determined to be 5.31%.

Example 4 Preparation of ammonium tungstate from PIB mono-succinimide polyamine dispersant To a solution of 50.2 g dispersant (60% active in process oil; PIBmw = 2100; TBN = 87.8) and 50.1 g 7.6 g of tungstic acid and 7.6 g of water are charged with process oil. The stirred paste is then heated to 120 ° C and water distillation begins. The temperature is then slowly increased to 160 ° C and the reaction begins to turn green as distillation continues. When distillation ceases, vacuum is applied to the system and the reaction continues at 160 ° C with stirring until the reaction mixture turns brown. It is then hot filtered through diatomaceous earth. The tungsten content was determined to be 2.6 mass percent.

Example 5 Preparation of Ammonium Tungstate from PIB Monosuccinimide Polyamine Dispersant To a solution of 46.5 g monosuccinimide dispersant (60% active in process oil; PIBmw = 2100; TBN = 44.30) and 46.5 g of process oil is charged 9.0 g of tungstic acid and 10.6 g of water. The stirred paste is then slowly heated to 160 ° C with reflux. At 160 ° C distillate is collected causing a color change to olive green. When distillation ceases, vacuum is applied to the system and the reaction continues at 160 ° C with stirring until the reaction mixture turns brown. It is then hot filtered through a diatomaceous earth. The tungsten content was determined to be 4.4 weight percent.

Example 6 Preparation of Ammonium Tungstate from PIB Monosuccinimide Polyamine Dispersant To a solution of 4 9.8 g of monosuccinimide dispersant (60% active in process oil; PIBmw = 1000; TBN = 33.52) and 49.9 g of process oil are charged 19.6 g of tungstic acid and 15.1 g of water. The stirred paste is then slowly heated to 160 ° C and the distillate collected as the mixture turns dark green. When distillation ceases, vacuum is applied to the system and the reaction continues at 160 ° C with stirring until the reaction mixture turns brown. It is then hot filtered through a diatomaceous earth. Tungsten content was determined to be 8.72 weight percent.

Example 7 Preparation of ammonium tungstate from PIB bis-succinimide polyamine dispersant To a solution of 67.42 g of bis-succinimide dispersant (HiTEC® 644) (approximately 75% active in process oil; TBN = 47, 20) and 16.8 g of process oil are charged 14.24 g of tungstic acid and 9.35 g of water. The stirred paste is then heated at 99 - 101 ° C for 1.5 hours. It is then slowly heated at 160 ° C for 2.5 hours and maintained at 160 ° C for 1.5 hours while the distillate is collected and the mixture turns green. When distillation ceases, vacuum is applied to the system and the reaction continues at 160 ° C with stirring until the reaction mixture turns brown. It is then filtered hot through a diatomaceous earth. Tungsten content was determined to be 4.52 weight percent.

Example 8 Preparation of Ammonium Tungstate from PIB Monosuccinimide Polyamine Dispersant To a 50.5 g solution of a mono succinimide dispersant (60% active in process oil; PIBmw = 2100; TBN = 44.30) and 50.5 g of process oil are charged 5.01 g of tungstic acid and 4.22 g of water. The stirred paste is then slowly heated to 160 ° C, at which point the distillate is collected as the mixture turns dark green. When distillation ceases, vacuum is applied to the system and the reaction continues at 160 ° C with stirring until the reaction mixture turns brown. It is then hot filtered through a diatomaceous earth. Tungsten content was determined to be 1.9 percent by mass.

To illustrate various functional fluid compositions, specifically lubricating compositions, comprising the compositions of the present invention, the following illustrative examples are provided. The following examples are provided for illustrative purposes only and not to limit the scope of the invention where that scope is set forth in the claims only.

Oxidation stability test Oxidation stability was measured by pressurized differential scanning calorimetry (PDSC) as described by ASTM D6186. PDSC measures oxidation stability by detecting exothermic heat release when the antioxidant capacity of a lubricant composition is depleted and the base oil enters the oxidative chain reaction known as auto-oxidation. The time from the start of the experiment to self-oxidation is known as oxidation induction time (ILO). Thus, longer ILOs indicate greater oxidative stability and antioxidant capacity. Example 9 Linear branched Cu (Cu) di (alkyl) ammonium tungstate of Example 1 and VANLUBE® 961, an octylated / butylated secondary diarylamine provided by R.T. Vanderbilt Company, Inc., were mixed with Group I Unocal 90 base oil as shown in Table 2. The oxidation stability of these oils was determined by PDSC as described in ASTM D 6186. Data, as summarized in Table 2, show that ammonium tungstate alone provides almost no protection against oxidation while VANLUBE® 961, as expected, is an efficient antioxidant. Most importantly and unexpectedly, the data show that the antioxidant capacity of VANLUBE® 961 is significantly increased in the presence of ammonium tungstate over a wide range of secondary diarylamine: tungsten content ratio. The ratios between 16: 1 and 5: 1 are particularly effective.

Example 10 Branched and linear Cu-C1-4 di (alkyl) ammonium tungstate of Example 1 and VANLUBE® 81, a m.p.-dioctylated secondary diarylamine provided by R.T. Vanderbilt Company, Inc., were mixed with Group I base oil

Unocal 90, as shown in Table 3. The oxidation stability of these oils was determined by PDSC as described in ASTM D 6186. The data, as summarized in Table 3, shows that the ammonium tungstate of example 1 alone provides almost no oxidation protection while VANLUBE® 81, as expected, is an efficient antioxidant. Most importantly and unexpectedly, the data show that the antioxidant capacity of VANLUBE® 81 is significantly increased in the presence of ammonium tungstate.

Table 2 Example 1 is branched and linear di (alkyl) ammonium tungstate with tungsten content of 26.4 weight percent. VANLUBE® 961 is an octylated / butylated secondary diarylamine provided by R.T. Vanderbilt Company Inc.

Example 3 is branched and linear Cn-C1- di (alkyl) ammonium tungstate with 26.4 weight percent tungsten content, VANLUBE® 81 is a p, p'-dioctyl secondary diarylamine provided by R.T. Vanderbilt Company Inc.

Example 11 Branched and linear C11-C14 di (alkyl) ammonium tungstate of Example 1 and VANLUBE® SL, an octyl / styrene secondary diarylamine provided by R.T. Vanderbilt Company, were mixed with Group 1 Unocal 90 base oil as shown in Table 4. The oxidation stability of these oils was determined by PDSC as described in ASTM D 6186. Data, as summarized in Table 4, show that Ammonium tungstate provides almost no protection against oxidation while VANLUBE® SL, as expected, is an efficient antioxidant. Most importantly and unexpectedly, the data show that the antioxidant capacity of VANLUBE® SL is significantly increased in the presence of ammonium tungstate.

Table 4 Example 1 is branched and linear C11 -C14 di (alkyl) ammonium tungstate having a tungsten content of 26.4 weight percent. VANLUBE® SL is an octylated / styrene secondary diarylamine provided by R.T. Vanderbilt Company Inc.

Example 12 Monosuccinimide Polyamine Dispersant Ammonium Tungstate PIB of Example 2 and various secondary diarylamines were mixed with Group I Unocal 90 base oil as shown in Table 5. The oxidation stability of these oils was determined by PDSC as described. in ASTM D 6186. The data, as summarized in table 5, show that ammonium tungstate provides almost no protection against oxidation while secondary diarylamines, as expected, are an efficient antioxidant. Most importantly and unexpectedly, the data show that the antioxidant capacity of all secondary diarylamines is significantly increased in the presence of ammonium tungstate.

Example 5 is ammonium tungstate of mono-succinimide PIB polyamine dispersant with tungsten content of 9.67 weight percent.

Example 13 Monosuccinimide Polyamine Dispersant Ammonium Tungstate PIB of Example 2 and VANLUBE® SL, an octylated / styrene secondary diarylamine provided by R.T. Vanderbilt Company were mixed with Group I Unocal 90 base oil as shown in Table 6. The oxidation stability of these oils was determined by PDSC as described in ASTM D 6186. Data shows that the dispersing tungstate of Example 2 enhances the ability antioxidant over a wide range of secondary diarylamine and high ammonium tungstate concentrations that will provide lubricant compositions with effective dispersant levels and wear protection that are close to typical.

Example 6 Ammonium tungstates of PIB succinimide polyamine dispersants of Examples 2, 3, 4, 5, 6, 7 and 8 and VANLUBE® SL, an octyl / styrene secondary diarylamine provided by R.T. Vanderbilt Company were mixed with Group I Unocal 90 base oil as shown in Table 7. The oxidation stability of these oils was determined by PDSC as described in ASTM D 6186. Data show that all ammonium tungstates are effective synergists, independent of molecular weight GDP, TBN, preparation method and tungsten charge, as summarized in Table 8.

Table 7 Table 8 1monosuccinimide is Chevron ORONITE® OLOA 371 2monosuccinimide is Chevron ORONITE® OLOA 11000. 3bisuccinimide is HiTEC® 644 provided by Afton Chemical Company.

Claims (11)

1. Lubricating composition characterized by the fact that it comprises a greater amount of a lubricating oil and 0.5 - 2.0 weight percent of a secondary diarylamine and an organoammonium tungstate in an amount providing 50-3000 ppm of tungsten, wherein organoammonium tungstate is a reaction product of (a) a source of tungsten and (b) di- (straight and branched Cji-Cn alkyl) amine or a mono- or bis-substituted succinimide of formula: in where x = 2-6, n = 0-10, R1 and R6 are independently hydrogen, straight or branched alkyl groups containing from 1 to 25 carbon atoms, alkoxy groups containing from 1 to 12 carbon atoms, alkylene groups containing from 2 to 6 carbon atoms, and hydroxyl or amino alkylene groups containing from 2 to 12 carbon atoms, and R11 is polyisobutenyl having molecular weight ranging from 800-2500 grams per mol. Lubricating composition according to claim 1, characterized in that the organoammonium tungstate is present in an amount providing approximately 50 - 50,000 ppm tungsten. Lubricating composition according to claim 1, characterized in that the organoammonium tungstate is present in an amount providing approximately 500 - 3,000 ppm tungsten. Lubricating composition according to claim 1, characterized in that the ratio of secondary dialysine to tungsten mass is approximately 75: 1 to approximately 1: 3. Lubricating composition according to Claim 4, characterized in that the mass ratio of secondary diarylamine to tungsten is approximately 35: 1 to approximately 1: 3. Lubricating composition according to claim 5, characterized in that the mass ratio of secondary diarylamine to tungsten is approximately 16: 1 to approximately 2: 1. Lubricating composition according to claim 1, characterized in that the secondary diarylamine comprises wherein R 1, R 1, R 1 and R 2; individually represent independently hydrogen, alkyl, aralkyl, aryl and alearyl groups having 1 to about 20 carbon atoms per group, where X is (CH; Jn, SouOenéOa 2, or X are two hydrogens attached to their respective carbons in a secondary diphenylamine structure. Lubricating composition according to claim 7, characterized in that at least one of R1, R2, R3 and R4 is individually independently chosen from hydrogen, 2-methylpropenyl, 2,4,4-trimethylpentenyl, styrenyl and nonyl. . Lubricating composition according to claim 7, characterized in that the secondary diarylamine is chosen from octylated / butylated secondary diarylamine, p, p'-dioctylated secondary diarylamine and styrene / octylated secondary diarylamine. Lubricating composition according to claim 1, characterized in that the organoammonium tungstate is a reaction product of (a) a tungsten source and (b) di (C11 -C14 linear and branched alkyl) amine. Lubricating composition according to claim 1, characterized in that the tungsten source is chosen from tungstic acid, tungsten trioxide, ammonium tungstate, ammonium paratungstate, sodium tungstate dihydrate, calcium tungstate. and ammonium metatungstate.